Hello condo1, if your sure that the odor is not a dead animal, I would recommend a smoke test by a licenced plumber, if there is cleanout on your sewerline outside the building a smoke test would show you if there is a leak on the drainage system in your home, you would be able to see smoke come out of any spot that would be allowing sewer gasses out of a crack, or void. like beneath the toilet, shower drain, beneath the tub, ect.
if its a dead animal double up on air freshener for a while.

Goodluck------Zeke